1. Field of the Technology
The present invention relates generally to Push-To-Talk (PTT) communications, and more particularly to methods and apparatus for providing PTT data buffering support indications from mobile devices and PTT data buffering control by wireless communication networks.
2. Description of the Related Art
A mobile communication device, such as a cellular telephone or mobile station, is capable of making and receiving voice calls and/or sending and receiving data over a wireless communication network. Recent developments have given such mobile stations the ability to communicate in “push-to-talk” (PTT) modes using Push-to-talk over Cellular (PoC) technology. PoC communication utilizes Voice-over-IP (VoIP) techniques which involve the communication of data packets carrying voice information.
PoC communication is adapted for one-to-one talks or group talks which are session-based. The end user of a mobile station may send an “invitation” for PoC communication to other potential “participants” who may “accept” or ignore the invitation. When an initiation is accepted, a PoC session is created between the two participants. Further acceptances of the invitation may expand the session into a group session having more than two participants.
In such networks, when the PTT switch is pressed at the mobile station, the end user is not able to immediately speak into the microphone. The end user must wait for some time delay period after the PTT switch depression in order to speak. This time delay period may be caused by physical radio channel setup, mobile paging, and PTT session setup activities. This delay is an inconvenience for end users in PTT communications, who may have to wait up to around eight seconds in some cases to talk after depressing the PTT switch.
In proposed Open Mobile Alliance (OMA) specifications, buffering in the network is specified to work-around the connection delay while the base station is paging the other party (or parties). However, no such technique is described for buffering at the handset to allow the origination party to talk immediately after PTT switch actuation. The following text is from the OMA standard that addresses the issue between the PoC Server and a terminating side “user B”, which does not address the issue between an originating side “user A” and the PoC Server:                the PoC Server sends the final response after receiving the first auto-answer response from the terminating side and adds the Unconfirmed Indication to the final response. In this case the media buffering is supported and the Talk Burst confirm is sent after the first auto answer response is received. If buffering is not supported the Talk Burst confirm is sent after the first response to the invitation is received.        [if] a SIP 183 “Session Progress” response is received from the terminating side before a SIP 200 “OK” response is sent, PoC Server performing the Controlling PoC Function, sends a SIP 200 “OK” response to the PoC Client. In this flow the media buffering is supported and the TBCP Talk Burst Granted is sent after the SIP 183 “Session Progress” is received. If buffering is not supported the TBCP Talk Burst Granted is sent after the SIP 200 “OK” is received.        
These above-described techniques relate to buffering in the network and do not address the time delay between PTT switch actuation of the handset and the time to begin talking. Note there is a gap in this technique even for some of the user B's communications. The network only buffers media until the first user B is accepted, and the buffered media are sent to all users that accepted. Thus, some portion of the media data may be missed for users 2 to N.
For PTT communications, especially higher-bandwidth media communications (e.g. video), the network may be overburdened with the buffering needs of the many mobile stations operating in the network and the number of terminals supportable by the network is reduced significantly, which would result in significant additional infrastructure investment costs. If a mobile station were also provided with buffering for PTT communications, there are issues regarding control and coordination of buffering activities.
Accordingly, there is a resulting need for methods and apparatus for facilitating PTT communications with use of buffering that overcome the deficiencies of the prior art.